The purpose of this study is to compare the usefulness of these drugs in controlling psoriasis. If you are eligible for the study, you will pick two lesions that are alike, one lesion will get .1G of calcipotriene ointment, the other lesion will get exorex cream a few minutes later. All lesions will be photographed before the therapy, every 2 to 4 weeks after, and once again at the end of the study. A 10CC blood sample will be taken once a month. This study will last 2 to 4 months.